A numerical framework for fatigue lifetime prediction of complex welded structures

Ageing infrastructure has been a significant concern for different industrial sectors across Europe. Fatigue cracking is one of the most important damage mechanisms that affect structural health of welded steel structures. Fatigue assessment of welded details in large, complex structures is a difficult and time consuming task. In this paper a numerical framework for fatigue assessment of welded details is presented. In view of industrial applications, automated hot spot stress algorithms for plate and tubular joints were developed and integrated in the framework. The framework provides practicing engineers with an effective tool for fatigue assessment of different components in conformity with leading design codes. Furthermore, apart from Miner’s rule the framework allows easy implementation of different non-linear damage accumulation models in order to account for load interaction and load sequence effects

Very high intact-protein formula successfully provides protein intake according to nutritional recommendations in overweight critically ill patients : a double-blind randomized trial

Background: Optimal energy and protein provision through enteral nutrition is essential for critically ill patients. However, in clinical practice, the intake achieved is often far below the recommended targets. Because no polymeric formula with sufficient protein content is available, adequate protein intake can be achieved only by supplemental amino acids or semi-elemental formula administration. In the present study, we investigated whether protein intake can be increased with a new, very high intact-protein formula (VHPF) for enteral feeding. Methods: In this randomized, controlled, double-blind, multicenter trial, 44 overweight (body mass index = 25 kg/m(2)) intensive care unit patients received either a VHPF (8 g/100 kcal) or a commercially available standard high protein formula (SHPF) (5 g/100 kcal). Protein and energy intake, gastrointestinal tolerance (gastric residual volume, vomiting, diarrhea, and constipation), adverse events, and serious adverse events were recorded. Total serum amino acid levels were measured at baseline and day 5. Results: The primary outcome, protein intake at day 5, was 1.49 g/kg body weight (95% CI 1.21-1.78) and 0.76 g/kg body weight (95% CI 0.49-1.03, P < 0.001) for VHPF and SHPF, respectively. Daily protein intake was statistically significantly higher in the VHPF group compared with the SHPF group from day 2 to day 10. Protein intake in the VHPF group as a percentage of target (1.5 g/kg ideal body weight) was 74.7% (IQR 53.2-87.6%) and 111.6% (IQR 51.7-130.7%) during days 1-3 and days 4-10, respectively. Serum amino acid concentrations were higher at day 5 in the VHPF group than in the SHPF group (P = 0.031). No differences were found in energy intake, measures of gastrointestinal tolerance, and safety. Conclusions: Enteral feeding with VHPF (8 g/100 kcal) resulted in higher protein intake and plasma amino acid concentrations than an isocaloric SHPF (5 g/100 kcal), without an increase in energy intake. This VHPF facilitates feeding according to nutritional guidelines and is suitable as a first-line nutritional treatment for critically ill overweight patients

51Cr-EDTA plasma clearance in children. One, two, or multiple samples?

Plasma disappearance curves using multiple blood samples are a recognized reference method for measuring glomerular filtration rate (GFR). However, there is no consensus on the protocol for this type of measurement. A two-compartment model is generally considered acceptable for the mathematical description of the concentration–time decay curve. The impact of the fitting procedure on the reported GFR has not been questioned. We defined 8 different fitting procedures to calculate the area under the curve, and from this area under the curve, the GFR. We applied the 8 fitting methods (all considering a full concentration–time curve) on the multiple sample data (8 samples) of 20 children diagnosed with Duchenne muscular dystrophy. We evaluated the effect (variability) on the reported GFR from the different fitting methods and compared these results with GFR-values calculated from late samples only (samples after 120 minutes) and from one-sample methods. In 6 out of 20 cases, the fitting methods on the full concentration–time curve resulted in very different reported GFR-values, mainly because some methods were not able to fit the data, or methods resulted in GFR-values ranging from 0 to 120 mL/min. The reported GFR-result therefore strongly depends on the fitting method, making the full concentration–time method less robust than expected. Compared with a consensus reference GFR, the late sample models did not show fitting issues and may therefore be considered as more robust. Also the one-sample methods showed acceptable accuracy. The late sample methods (using 3 time-points) provide robust and reliable methods to determine GFR

Epidemiology of intra-abdominal infection and sepsis in critically ill patients: "AbSeS", a multinational observational cohort study and ESICM Trials Group Project.

PURPOSE: To describe the epidemiology of intra-abdominal infection in an international cohort of ICU patients according to a new system that classifies cases according to setting of infection acquisition (community-acquired, early onset hospital-acquired, and late-onset hospital-acquired), anatomical disruption (absent or present with localized or diffuse peritonitis), and severity of disease expression (infection, sepsis, and septic shock). METHODS: We performed a multicenter (n = 309), observational, epidemiological study including adult ICU patients diagnosed with intra-abdominal infection. Risk factors for mortality were assessed by logistic regression analysis. RESULTS: The cohort included 2621 patients. Setting of infection acquisition was community-acquired in 31.6%, early onset hospital-acquired in 25%, and late-onset hospital-acquired in 43.4% of patients. Overall prevalence of antimicrobial resistance was 26.3% and difficult-to-treat resistant Gram-negative bacteria 4.3%, with great variation according to geographic region. No difference in prevalence of antimicrobial resistance was observed according to setting of infection acquisition. Overall mortality was 29.1%. Independent risk factors for mortality included late-onset hospital-acquired infection, diffuse peritonitis, sepsis, septic shock, older age, malnutrition, liver failure, congestive heart failure, antimicrobial resistance (either methicillin-resistant Staphylococcus aureus, vancomycin-resistant enterococci, extended-spectrum beta-lactamase-producing Gram-negative bacteria, or carbapenem-resistant Gram-negative bacteria) and source control failure evidenced by either the need for surgical revision or persistent inflammation. CONCLUSION: This multinational, heterogeneous cohort of ICU patients with intra-abdominal infection revealed that setting of infection acquisition, anatomical disruption, and severity of disease expression are disease-specific phenotypic characteristics associated with outcome, irrespective of the type of infection. Antimicrobial resistance is equally common in community-acquired as in hospital-acquired infection

Thermodynamics and hydrodynamics of \u3csup\u3e3\u3c/sup\u3eHe-\u3csup\u3e4\u3c/sup\u3eHe mixtures

\u3cp\u3eThe specific heat of liquid \u3csup\u3e3\u3c/sup\u3eHe–\u3csup\u3e4\u3c/sup\u3eHe mixtures is usually written in terms of the sum of the specific heat of a \u3csup\u3e3\u3c/sup\u3eHe-quasiparticle gas and the specific heat of the pure \u3csup\u3e4\u3c/sup\u3eHe component. The thermodynamics based on this starting point is derived. Relations of important quantities and their low- and high-temperature limits are given. These are used to derive expressions for the velocity of second sound. This latter quantity is a very important source of information for the Fermi gas properties. Finally, the Fermi gas parameters are summarized in the chapter. The experimental aspects of the \u3csup\u3e3\u3c/sup\u3eHe–\u3csup\u3e4\u3c/sup\u3eHe hydrodynamics are treated. The appearance of mutual friction that has long been neglected in this field is discussed, together with the properties of the critical velocities. The phenomenological equations of motion are given. The occurrence of mutual friction is a strong indication that \u3csup\u3e4\u3c/sup\u3eHe vortices play an important role in \u3csup\u3e3\u3c/sup\u3eHe–\u3csup\u3e4\u3c/sup\u3eHe hydrodynamics. From the equation of motion of quantized \u3csup\u3e4\u3c/sup\u3eHe vortices, the observed cubic velocity dependence of the \u3csup\u3e4\u3c/sup\u3eHe chemical potential difference is explained on purely dimensional grounds. A differential equation is given from which the temperature profile in a cylindrical tube in which \u3csup\u3e3\u3c/sup\u3eHe flows through superfluid \u3csup\u3e4\u3c/sup\u3eHe can be calculated.\u3c/p\u3

Fatigue assessment of a steel truss bridge based on multi-dimensional finite element modelling

This paper presents a multidimensional finite element modelling approach for the fatigue assessment of welded railway bridges based on a case study of a railway bridge in Belgium. The nominal stress approach of Eurocode 3 is compared to a hot spot stress based fatigue life calculation for the standardized fatigue load models for railway traffic. Hot spot stresses are calculated with an in-house developed framework that allows automated determination of hot spot stresses. It is discussed how this work can fit in a larger decision support system in the scope of structural health monitoring. The presented approach proves to be better for decision support compared to the conventional approach in the Eurocode

Fatigue lifetime prediction of complex welded structures

Lifetime assessment of dynamically loaded structures is essential towards decision support for quantification of lifetime extension and optimization of predictive maintenance. The core of our current research is the development of numerical tools for structural and fatigue analysis of welded steel structure

Fatigue lifetime prediction of complex welded structures

Lifetime assessment of dynamically loaded structures is essential towards decision support for quantification of lifetime extension and optimization of predictive maintenance. Fatigue failures can have catastrophic consequences, both social and environmental. Reliable prediction of fatigue failure will lead to a substantial reduction of operation and maintenance costs for players in different sectors. The core of our current research is the development of numerical tools for structural and fatigue analysis of welded steel structures. Using finite element modeling, stress concentrations in large structures can be located and quantified. A custom developed python framework is then used to estimate the remaining lifetime of the structure

A Numerical framework for fatigue lifetime prediction of complex welded structures

Ageing infrastructure is of major concern for different industrial sectors across Europe. Fatigue cracking is one of the most important damage mechanisms that affect structural health of welded steel structures. Fatigue assessment of welded details in large, complex structures is a difficult and time consuming task. In this paper a numerical framework for fatigue assessment of welded details is presented. In view of industrial applications, automated hot spot stress algorithms for plate and tubular joints were developed and integrated in the framework. The framework provides practicing engineers with an effective tool for fatigue assessment of different components in conformity with leading design codes. Furthermore, apart from Miner’s rule the framework allows easy implementation of different non-linear damage accumulation models in order to account for load interaction and load sequence effects